Wireless path control method, wireless communication system, wireless node and wireless path control program

Abstract

A control signal for selecting a parent node in a tree path is transmitted from a first wireless node (#0) among a plurality of wireless nodes (#0 to #7) constituting a backhaul network (9), and each of a plurality of second wireless nodes (#1 to #7) selects one of the transmission source nodes of each of the plurality of control signals as a parent node based on an index indicating the radio wave propagation quality of the path propagated from each of the plurality of control signals received from different paths. In addition, a fixed wireless node (#1 to #3 and #5 to #7) among the plurality of second wireless nodes (#1 to #7) transmits the received control signal to other second wireless nodes, and a mobile wireless node (#4) among the plurality of second wireless nodes (#1 to #7) terminates the received control signal.

Description

Technical Field

[0001] The invention relates to a wireless path control method, a wireless communication system, a wireless node and a wireless path control program. Background Art

[0002] In existing cellular communication systems, base stations that provide wireless access lines for user devices are often connected to a backbone network (sometimes also referred to as a "core network") via a wired backhaul (BH) network.

[0003] On the other hand, as a form of realizing the next generation of mobile communications, a system or network that connects multiple wireless nodes (eg, base stations or access points) providing a wireless communication area with a radius of tens of meters through wireless multi-hop is being studied.

[0004] For example, by making the BH network, which is one of the infrastructures of mobile communications, wireless through wireless multi-hop, it is no longer necessary to lay wired cables, and the installation cost required for introducing a wireless communication system can be reduced.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2005-143046

[0008] Patent Document 2: International Publication No. 2011 / 105371 Summary of the invention

[0009] Problem that the invention aims to solve

[0010] In many cases, the infrastructure of a BH network is composed of fixed wireless nodes such as base stations. Therefore, when the infrastructure of a BH network includes wireless nodes that can move (for example, terminal devices), path control may become inappropriate. For example, when a terminal device is set as a wireless node that performs signal relay processing through path control in a BH network, the power consumption of the terminal device increases with the relay processing.

[0011] One of the objects of the present invention is to implement appropriate path control when the infrastructure of a backhaul network includes mobile wireless nodes.

[0012] Solutions to the problem

[0013] A wireless path control method according to one embodiment of the present invention comprises the following steps: a control signal for selecting a parent node in a tree path is sent from a first wireless node among a plurality of wireless nodes constituting a backhaul network; each of a plurality of second wireless nodes among the plurality of wireless nodes that are different from the first wireless node selects one of the sending source nodes of each of the plurality of control signals as a parent node based on an indicator representing the radio wave propagation quality of the path propagated from each of the plurality of control signals received from different paths; a fixed wireless node among the plurality of second wireless nodes sends the received control signal to other second wireless nodes, and a movable wireless node among the plurality of second wireless nodes terminates the received control signal.

[0014] In addition, a wireless communication system of one embodiment of the present invention includes: a first wireless node, which is a first wireless node among multiple wireless nodes constituting a backhaul network, and sends a control signal for selecting a parent node in a tree path; and multiple second wireless nodes, which are multiple second wireless nodes among the multiple wireless nodes that are different from the first wireless node, and based on an indicator representing the quality of radio wave propagation of a path propagated from each of the multiple control signals received from different paths, one of the sending source nodes of each of the multiple control signals is determined as a parent node, a fixed wireless node among the multiple second wireless nodes sends the received control signal to other second wireless nodes, and a movable wireless node among the multiple second wireless nodes terminates the received control signal.

[0015] In addition, a wireless communication node of one embodiment of the present invention is one of a plurality of second wireless nodes different from a first wireless node among a plurality of wireless nodes constituting a backhaul network, and includes: a setting unit, which sets information indicating whether the second wireless node is capable of moving into a storage unit; a receiving unit, which receives a control signal sent by the first wireless node for selecting a parent node in a tree path; a determining unit, which determines one of the sending source nodes of each of the plurality of control signals as a parent node based on an indicator indicating the quality of radio wave propagation of the path propagated from each of the plurality of control signals received from different paths; and a sending unit, which sends the received control signal when the information does not indicate that it is capable of moving, and terminates the received control signal when the information indicates that it is capable of moving.

[0016] In addition, a wireless path control program of one embodiment of the present invention causes a processor of one of a plurality of second wireless nodes different from a first wireless node among a plurality of wireless nodes constituting a return network to perform the following processing: setting information indicating whether the second wireless node is capable of moving into a storage unit; receiving a control signal for selecting a parent node in a tree path sent by the first wireless node; based on an indicator indicating the quality of radio wave propagation of a path propagated from each of the plurality of control signals received from different paths, determining one of the sending source nodes of each of the plurality of control signals as a parent node; if the information does not indicate that the node is capable of moving, sending the received control signal; if the information indicates that the node is capable of moving, terminating the received control signal.

[0017] Effects of the Invention

[0018] The present invention enables appropriate path control when the infrastructure of the backhaul network includes mobile wireless nodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a block diagram showing a configuration example of a wireless communication system according to one embodiment.

[0020] Figure 2 This is a diagram showing an example of a connection form between nodes according to one embodiment together with a protocol stack of each node.

[0021] Figure 3 This is a block diagram showing an example of the hardware configuration of a node according to one embodiment.

[0022] Figure 4 This is a block diagram showing an example of a functional structure of a node according to one embodiment.

[0023] Figure 5 It is shown Figure 4 A block diagram of an example of a functional structure of a control unit illustrated in FIG.

[0024] Figure 6 It is shown that by Figure 1 FIG. 4 is a diagram showing an example of a tree path constructed by tree path control performed by each node of a backhaul (BH) network illustrated in FIG.

[0025] Figure 7 It is shown Figure 6 2 is a diagram showing an example of tree path control when one of the slave nodes (SN) forming the tree path is set to the V mode (vehicular mode).

[0026] Figure 8 It is shown Figure 7 A diagram showing an example of tree path control when VSN (V-mode SN) moves.

[0027] Fig. 9 It is shown Figure 7 A diagram showing an example of tree path control in the case of VSN movement.

[0028] Fig.10 This is a flowchart showing an example of operation of a core node (CN) including tree path control according to one embodiment.

[0029] Fig.11 This is a flowchart showing an example of the operation of the SN including the tree path control according to one embodiment.

[0030] Fig.12 This is a flowchart showing an example of operation of the SN (VSN) set to the V mode according to one embodiment. DETAILED DESCRIPTION

[0031] The following describes the embodiments with reference to the accompanying drawings as appropriate. In the entire specification, the same elements are given the same reference numerals unless otherwise specified. Figure 1 The matters described below are used to illustrate exemplary embodiments and are not intended to represent the only embodiment. For example, when the order of actions is shown in the embodiment, the order of actions may be appropriately changed as long as the overall action does not cause any contradiction.

[0032] When multiple embodiments and / or variations are exemplified, part of the structure, function and / or action in a certain embodiment and / or variation may be included in other embodiments and / or variations, or may be replaced by corresponding structure, function and / or action in other embodiments and / or variations, within the scope without causing any contradiction.

[0033] In addition, in the embodiments, detailed descriptions beyond the necessary limit are sometimes omitted. For example, in order to avoid the description from becoming unnecessarily lengthy and / or the technical matters or concepts becoming unclear, detailed descriptions of well-known or well-known technical matters are sometimes omitted so that those skilled in the art can understand them easily. In addition, repeated descriptions of substantially the same structures, functions and / or actions are sometimes omitted.

[0034] The attached drawings and the following description are provided to help understand the embodiments, and are not intended to limit the subject matter described in the claims. In addition, the terms used in the following description may also be appropriately replaced with other terms to help those skilled in the art understand.

[0035] <System Configuration Example>

[0036] Figure 1 is a block diagram showing a configuration example of a wireless communication system according to an embodiment. Figure 1 The wireless communication system 1 shown has a plurality of nodes 3. Figure 1 In FIG. 1 , 15 nodes 3 are shown as non-limiting examples and are represented by node numbers #0 to #14. The number of nodes 3 may be 2 or more and less than 14, or 16 or more.

[0037] Each node 3 is an example of a wireless device capable of wireless communication. Therefore, each node 3 may also be referred to as a "wireless node 3". In wireless communication, a communication protocol based on (or based on) wireless LAN (Local Area Network) related specifications such as IEEE802.11b / g / a / n / ac / ad / ay may be applied.

[0038] Each node 3 forms an area where wireless communication is possible. The "area where wireless communication is possible" may also be referred to as a "wireless communication area", "wireless area", "communication area", "service area", "coverage area" or "cover area". It may also be considered that the wireless communication area formed by the node 3 based on the wireless LAN association specification corresponds to a "cell" as a name in cellular communication. It may also be considered that, for example, the wireless communication area formed by each node 3 is equivalent to a "femtocell" classified as a "small cell".

[0039] Each node 3 can wirelessly communicate with another node 3 when it is located in the service area of ​​another node 3. The multiple nodes 3 form, for example, a wireless backhaul (BH) network 9 that wirelessly relays communication between the backbone network 5 and the terminal device 7. The "wireless" in the "wireless BH network" may be omitted and it may be referred to as a "BH network".

[0040] The “BH network” may also be referred to as a “relay network.” Each node 3 that is an entity of the BH network 9 may also be referred to as a “relay node.”

[0041] Exemplarily, the backbone network 5 is a large-scale communication network such as the Internet. The "backbone network" may also be called a "core network" or a "global network".

[0042] The path or section where the wireless signal is transmitted in the BH network 9 may be referred to as a "wireless BH communication path", "wireless BH transmission path", "wireless BH line", "wireless BH connection" or "wireless BH channel". In these terms, "wireless" may be omitted, and "BH" may be referred to as "relay".

[0043] On the other hand, for example, a section in which a wireless signal is transmitted between the terminal device 7 and the BH network 9 may be referred to as a "wireless access line" or a "wireless access channel." In these terms, "wireless" may be omitted.

[0044] In the following description, the term "signal" may be replaced by a term that temporally divides a signal into units such as "frame" or "packet".

[0045] Different frequencies (channels) may be allocated to the wireless BH line and the wireless access line. As a non-limiting example, a frequency (channel) in the 5 GHz band (eg, 5.15 GHz to 5.85 GHz) may be allocated to the BH line.

[0046] A frequency (channel) in the 2.4 GHz band (for example, 2.412 GHz to 2.472 GHz) may be allocated to the access line. A frequency in the 5 GHz band may also be allocated to the access line as long as it is different from the frequency allocated to the BH line.

[0047] In the 5 GHz segment, for example, at least one of a 5.2 GHz segment (W52: 5150 MHz to 5250 MHz), a 5.3 GHz segment (W53: 5250 MHz to 5350 MHz), and a 5.6 GHz segment (W56: 5470 MHz to 5725 MHz) may be included.

[0048] In W52, the number of channels available is 36ch, 40ch, 44ch, and 48ch. In W53, the number of channels available is 52ch, 56ch, 60ch, and 64ch. In W56, the number of channels available is 11 channels, 100ch, 104ch, 108ch, 112ch, 116ch, 120ch, 124ch, 128ch, 132ch, 136ch, and 140ch.

[0049] Therefore, for example, when one or two frequency segments among W52, W53, and W56 are allocated to the access line, the remaining one or two frequency segments among W52, W53, and W56 that are not allocated to the access line may be allocated to the BH line.

[0050] Some of the multiple nodes 3 may be connected to the backbone network 5 by wire. Figure 1 In FIG. 5 , two nodes, namely, node #0 and node #8, are exemplified as being wiredly connected to the backbone network 5. For the wired connection, for example, a LAN cable or an optical fiber cable can be applied.

[0051] Node #0 and node #8 connected to the backbone network 5 by wire may be referred to as a "core node (CN)". Each node 3 other than CN #0 and #8 among the plurality of nodes 3 forming the BH network 9 may be referred to as a "slave node (SN)". For example, Figure 1 Node #1 to Node #7 and Node #9 to Node #14 are all SNs. CN3 is an example of a "first wireless node", and each SN3 is an example of a "second wireless node".

[0052] In addition, Figure 1 , #0 to #14 attached to each node 3 is an example of information for identifying each node 3 (hereinafter sometimes referred to as "node identification information"). The node identification information can be any information that can uniquely identify each node 3 in the same BH network 9, for example, a node number, an identifier of a device, or address information. A non-limiting example of address information is a MAC (Media Access Control) address.

[0053] The BH network 9 may have one or more tree structures (also referred to as "tree topology") with one CN3 (#0 or #8) as the root node. Figure 1 As shown, in the BH network 9, a first tree topology with CN#0 as the root node and a second tree topology with CN#8 as the root node can be constructed.

[0054] In other words, in the BH network 9, a "tree topology" can be constructed for each CN3. One or more "tree topologies" constructed in the BH network 9 can also be called a "tree cluster" or a "tree subcluster". In addition, in the BH network 9, the number of CN3 is not limited to two, but can be one or more than three.

[0055] In a tree topology, an SN3 without child nodes may be referred to as a "leaf node", and an SN3 with child nodes may be referred to as an "internal node". Figure 1SN#2, SN#3, SN#6, SN#7, SN#10, SN#11, SN#13, and SN#14 are all equivalent to "leaf nodes." In addition, SN#1, SN#4, SN#5, SN#9, and SN#12 are all equivalent to "internal nodes."

[0056] The wireless BH line may include a "downlink" from the core node 3 toward the leaf node 3, and an "uplink" from the leaf node 3 toward the core node 3. The "downlink" and "uplink" may also be referred to as "downlink (DL)" and "uplink (UL)" respectively, imitating the names in cellular communications.

[0057] The flow of signals (downlink signals) in the "downlink" may be referred to as "downstream", and the flow of signals (uplink signals) in the "uplink" may be referred to as "upstream". The "downlink signals" and "uplink signals" may each include control signals and data signals. The "control signals" may include signals that are not equivalent to "data signals".

[0058] In addition, it can also be considered that the "child node" is equivalent to the node connected downstream of a node (downstream node) when focusing on the "downlink". The node connected upstream of a node when focusing on the downlink can also be called the "parent node" or "upstream node". When focusing on the "uplink", the relationship between the "child node" (downstream node) and the "parent node" (upstream node) is reversed.

[0059] In addition, when focusing on the "downlink", the "core node" can also be called the "starting point node" or "starting point node", and the "leaf node" can also be called the "end point node" or "edge node". The "internal node" can also be called the "intermediate node" or "relay node".

[0060] The tree-structured path (tree topology) in the BH network 9 can be constructed, for example, based on the metric of the path from CN3 to a specific SN3 (hereinafter sometimes referred to as "path metric"). In the path metric, an index representing the quality or performance of radio wave propagation in the wireless section from CN3 to a specific SN3 (hereinafter referred to as "propagation quality index") can be used.

[0061] Non-limiting examples of propagation quality indicators include received power or received strength of wireless signals (eg, RSSI; Received Signal Strength Indicator), radio wave propagation loss, and propagation delay, etc. "Radio wave propagation loss" may also be referred to as "path loss."

[0062] As the propagation quality index, one or a combination of two or more selected from the above index candidates may be used. In addition, in the present embodiment, an index related to the path distance, such as the number of hops, may not be used as the propagation quality index.

[0063] For example, by transmitting a signal (eg, a control signal) from CN3 as a starting point, the radio wave propagation loss in each wireless section between the control signal transmitting node 3 and the receiving node 3 can be obtained at the receiving node 3 .

[0064] Then, each receiving node 3 includes the obtained radio wave propagation loss information in the control signal and transmits it, so that the information (in other words, the cumulative value) of the cumulative radio wave propagation loss in the wireless section through which the control signal is propagated can be transferred between the nodes 3 .

[0065] Each node 3 calculates a path metric based on the cumulative radio wave propagation loss for each upstream node candidate as a transmission source of the control signal, and selects a node 3 showing the minimum path metric from the upstream node candidates. Thus, a tree-structured path is constructed that minimizes the radio wave propagation loss.

[0066] The tree-structured path (hereinafter sometimes referred to as a "tree-structured path") can be updated dynamically or adaptively by periodically or irregularly sending a control signal starting from CN3.

[0067] Hereinafter, the processing or control related to the construction and updating of such a tree path is sometimes simply referred to as "tree path control", or "dynamic tree path control" or "adaptive tree path control".

[0068] In addition, in the wireless BH line of this embodiment, downlink signals (e.g., data signals) can be periodically and intermittently transmitted from CN3 to the downstream of the tree path (in other words, waiting for a purposeful transmission standby time). Such periodic and intermittent transmission is sometimes called "IPT (Interminent Periodic Transmittion)".

[0069] In IPT, as described in the aforementioned Patent Document 1, the transmission period (in other words, the transmission interval or the transmission frequency) of the downlink signal sent by CN3 to the downstream is changed according to the frequency reuse interval. The frequency reuse interval indicates the length (distance) of the interval in which the occurrence of interference between nodes in the same path is suppressed and the same frequency can be repeatedly reused.

[0070] By setting a transmission cycle corresponding to the frequency reuse interval for CN3, for example, complicated congestion control can be eliminated, thereby improving the transmission capacity in the wireless BH line, in other words, improving the relay transmission efficiency. In addition, the utilization efficiency of frequency reuse in the BH network 9 can be improved.

[0071] For example, by setting a frequency reuse interval for CN3 that suppresses the occurrence of inter-node interference, the transmission volume observed at the leaf node can be kept above a certain fixed value even when a single frequency is used in a tree topology, without depending on the number of hops.

[0072] For the uplink, for example, SN3 transmits an uplink signal upstream at a transmission cycle linked to a transmission cycle corresponding to the frequency reuse interval of the downlink, thereby enabling an improvement in the transmission amount observed at CN3.

[0073] Therefore, for example, it is easy to allocate the same frequency (channel) to the downlink and uplink of the wireless BH line to realize TDMA or TDD. In addition, "TDMA" is the abbreviation of Time Division Multiple Access, and "TDD" is the abbreviation of Time Division Duplex.

[0074] Therefore, it is not necessary to use wireless IFs (interfaces) of different frequencies in the downlink and uplink of the wireless BH line, and a common wireless IF can be used. By using a common wireless IF, the size and / or cost of the node 3 can be reduced.

[0075] However, different frequencies may be allocated to the downlink and uplink of the wireless BH line. By allocating different frequencies to the downlink and uplink of the wireless BH line, for example, IPT control for implementing TDMA or TDD can be simplified. Even when different frequencies are allocated to the downlink and uplink, the frequency resource consumption in the BH network 9 is only the amount of the two channels of the downlink and uplink.

[0076] Furthermore, a portion of the downlink and / or uplink of the BH line may include a wired line. In the case where a portion of the downlink and / or uplink of the BH line includes a wired line, the path metric of the wired section may be calculated using a specified value (e.g., a minimum value) that is smaller than the propagation loss of the wireless section.

[0077] When the terminal device 7 is located in the service area of ​​a certain SN3, it is connected to one of the plurality of SN3 forming the BH network 9 through a wireless access line, thereby communicating with the backbone network 5 through the BH line. In addition, the terminal device 7 may be connected to any one of the SN3 (in the case of a wireless access line) through a wired line (wired IF). Figure 1 As a non-limiting example, the terminal device 7 may be a mobile terminal such as a mobile phone, a smart phone, or a tablet terminal.

[0078] In the wireless access line, any one of CDMA (Code Division Multiple Access), FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), OFDMA (Orthogonal Frequency Division Multiple Access), and SC-FDMA (Single Carrier Frequency Division Multiple Access) can be applied. OFDMA can be specifically implemented by wireless technologies such as IEEE802.11, IEEE802.16, LTE (Long Term Evolution), and LTE-Advanced.

[0079] MIMO (Multiple Input Multiple Output) technology using an antenna array having a plurality of antenna elements may be applied to all or part of the downlink and / or uplink in the wireless BH line and / or the wireless access line.

[0080] For example, beamforming using an antenna array may be performed in the downlink and / or uplink of any one or more of the sections between CN3 and SN3, between SN3 and SN3, and between SN3 and the terminal device 7.

[0081] In addition, in the following description, the term "transmission" of a signal can also be replaced by other terms such as "relay", "transfer", "propagation", "transmission", "routing" or "forwarding" of a signal. "Relay" of a signal can also be replaced by "bridge" of a signal.

[0082] In addition, the term "sending" a signal may include the meaning of "flooding", "broadcasting", "multicasting" or "unicasting" of a signal. It can also be considered that the term "connecting" a line means a state in which a wired and / or wireless communication link has been "established" or "connected".

[0083] The term "device" can also be interchangeably referred to as "circuit", "equipment", "unit" or "module". The term "interface (IF)" can also be interchangeably referred to as "adapter", "board", "card" or "module", "chip".

[0084] The term "terminal device" can also be interchangeably referred to as "mobile station", "mobile terminal", "subscriber station", "mobile unit", "subscriber unit", "wireless unit", "remote unit", "mobile device", "wireless device", "wireless communication device", "remote device", "mobile subscriber station", "access terminal", "portable terminal", "wireless terminal", "remote terminal", "handheld device", "user agent", "mobile client" or "client".

[0085] The node 3 and / or the terminal device 7 may also be an IoT (Internet of Things) device. Through IoT, wireless communication functions can be installed in various "things". Various "things" equipped with wireless communication functions can be connected to the backbone network 5 through wireless access lines and / or wireless BH lines to communicate.

[0086] For example, IoT devices may include sensor devices and measuring instruments (measurers) with wireless communication functions. Devices with sensing and / or monitoring functions, such as surveillance cameras and / or fire alarms equipped with sensor devices and / or measuring instruments, may also correspond to nodes 3 and / or terminal devices 7. Therefore, the BH network 9 may also correspond to a sensor network and / or a monitoring network, for example. In addition, wireless communications performed by IoT devices are sometimes referred to as "MTC (Machine Type Communications). Therefore, IoT devices are sometimes referred to as "MTC devices."

[0087] <An example of the protocol stack of node 3>

[0088] Figure 2 In FIG. 1 , an example of the connection form between nodes 3 is shown together with the protocol stack of each node 3. Figure 2 , CN3 connected to the backbone network 5 via a wired line, and two SN3 connected to CN3 via wireless BH lines in multiple hops are shown.

[0089] In addition, it can be considered that Figure 2 The CN3 example corresponds to Figure 1 CN#0, Figure 2 The two SN3s correspond to Figure 1 SN#1 and SN#5. In addition, terminal device 7 can be connected to SN#5 via a wireless access line.

[0090] like Figure 2 As shown, each of the nodes 3 has, for example, a protocol stack, which includes, for example, a physical (PHY) layer (layer 1: L1), a MAC (Medium Access Control: Media Access Control) layer (layer 2: L2), a relay layer, and upper layers above layer 3 (L3). The upper layer may include, for example, a TCP / IP layer and / or an application layer. "TCP / IP" is an abbreviation for "Transmission Control Protocol / Internet Protocol".

[0091] The "relay layer" is an intermediate layer between layer 2 and layer 3 in the protocol stack, and therefore may also be conveniently referred to as "layer 2.5 (L2.5)". The processing of the relay layer may include processing related to the already described "adaptive tree path control" and / or processing (or control) related to "IPT".

[0092] By positioning the "relay layer" as an intermediate layer between layer 2 and layer 3, it is not necessary to change the existing MAC layer processing, so it is easy to implement the "relay layer" processing. The relay layer processing can also be implemented in one or more ways selected from software, middleware, firmware and hardware.

[0093] The physical layer of node 3 provides, for example, one wired connection (wired port) and two wireless connections (wireless ports). Figure 2 In the diagram, the three ports are simply represented as three "PHY" ports. One of the two wireless ports is for the BH line, and the other of the two wireless ports is for the access line. "Port" can also be called "interface (IF)".

[0094] In addition, Figure 2 In order to visually facilitate the understanding of the correspondence between the MAC layer and the three PHY ports of the physical layer, the MAC layer is simply divided into three parts for representation. However, the processing of the MAC layer can be common to each PHY port.

[0095] exist Figure 2 When focusing on the flow of downlink signals, the downlink signal received by CN#0 from the backbone network 5 is sent from the wireless port used for the BH line to the downstream BH line via the wired port (L1), MAC layer (L2) and relay layer (L2.5) of CN#0.

[0096] The downlink signal sent by CN#0 to the BH line is received by the wireless port for the BH line in the next hop SN#1, and is sent from the wireless port for the BH line to the downstream BH line via the MAC layer and relay layer of SN#1.

[0097] The downlink signal sent from SN#1 to the downstream BH line is received by the wireless port for the BH line in the next hop, SN#5, and is sent from the wireless port for the access line to the terminal device 7 via the MAC layer of SN#5. The downlink signal sent from the BH line to the access line does not have to pass through the relay layer.

[0098] The uplink signal travels in a reverse path to the path of the downlink signal described above, and is transmitted from the terminal device 7 to the backbone network 5 via SN#5, SN#1, and CN#0.

[0099] <Node 3 Configuration Example>

[0100] (Hardware configuration example of node 3)

[0101] Next, refer to Figure 3 , an example of the hardware structure of node 3 is described. In addition, Figure 3 The structural example illustrated in FIG. 1 may be common to CN3 and SN3. Figure 3 As shown, the node 3 may include, for example, a processor 31 , a memory 32 , a storage 33 , an input / output (I / O) device 34 , wireless IFs 35 and 36 , a wired IF 37 , a wired IF 39 , and a bus 38 .

[0102] In addition, Figure 3 In the hardware configuration example illustrated in the figure, the hardware can be appropriately increased or decreased. For example, any hardware block can be appropriately added or deleted, divided, integrated in any combination, and the bus 38 can be added or deleted.

[0103] It can be considered that the wireless IF 35, the wireless IF 36 and the wired IF 37 (or the wired IF 39) correspond to Figure 2The two wireless ports (PHY ports) and one wired port are illustrated in the protocol stack.

[0104] The processor 31, the memory 32, the storage 33, the input / output device 34, the wireless IFs 35 and 36, and the wired IFs 37 and 39 are connected to, for example, a bus 38 so as to be able to communicate with each other. The number of the bus 38 may be one or more.

[0105] The node 3 may be provided with multiple processors 31. In addition, the processing in the node 3 may be performed by one processor 31 or multiple processors 31. In one or more processors 31, multiple processing may be performed simultaneously, in parallel, or successively, or by other methods. In addition, the processor 31 may be a single-core processor or a multi-core processor. The processor 31 may be implemented using more than one chip.

[0106] For example, one or more functions of the node 3 are implemented by reading the specified software into the hardware such as the processor 31 and the memory 32. In addition, "software" can also be replaced by other terms such as "program", "application", "engine" or "software module".

[0107] For example, the processor 31 reads and executes the program by controlling one or both of reading and writing of data stored in one or both of the memory 32 and the storage 33. In addition, the program may be provided to the node 3 by, for example, communication via an electrical communication circuit based on at least one of the wireless IF 35, the wireless IF 36, and the wired IF 37.

[0108] The program may be a program that causes a computer to execute all or part of the processing in the node 3. In response to the execution of the program code included in the program, one or more functions of the node 3 are realized. All or part of the program code may be stored in the memory 32 or the storage 33, or may be recorded as part of the operating system (OS).

[0109] For example, a program can contain specific implementations that will be passed later Figure 4 as well as Figure 5 The program code of the functional block to be described may also include the execution of the function to be executed later. Figure 10 to Figure 12 The program code of any one or more of the flowcharts described above. A program including such a program code can be simply referred to as a "radio path control program".

[0110] The processor 31 is an example of a processing unit, and controls the entire computer by running an OS, for example. The processor 31 may be configured using a central processing unit (CPU) including an interface with peripheral devices, a control device, a calculation device, registers, and the like.

[0111] In addition, the processor 31 reads one or both of a program and data from the storage 33 to the memory 32 and executes various processes.

[0112] The memory 32 is an example of a computer-readable storage medium, and can be constituted by at least one of ROM, EPROM, EEPROM, RAM, SSD, etc. In addition, "ROM" is the abbreviation of "Read Only Memory", "EPROM" is the abbreviation of "Erasable Programmable ROM", "EEPROM" is the abbreviation of "Electrically Erasable Programmable ROM", "RAM" is the abbreviation of "Random Access Memory", and "SSD" is the abbreviation of "Solid State Drive".

[0113] Memory 32 may also be called “registers,” “cache,” “main memory,” “working memory,” or “primary storage.”

[0114] The memory 33 is an example of a computer-readable storage medium, and may be composed of at least one of a CD-ROM (Compact Disc ROM: optical disc read-only memory), a hard disk drive (HDD), a floppy disk, an optical magnetic disk (e.g., a compact disk, a digital versatile disk, a Blu-ray (registered trademark) disk), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy disk, a magnetic tape, etc. The memory 33 may also be referred to as an "auxiliary storage device". The above-mentioned storage medium may also be, for example, a database, a server, or other appropriate medium including one or both of the memory 32 and the memory 33.

[0115] The input / output (I / O) device 34 is an example of an input device that receives input of a signal from the outside of the node 3, and an output device that outputs a signal from the node 3 to the outside. For example, the input device may include one or more of a keyboard, a mouse, a microphone, a switch, a button, and a sensor. For example, the output device may include one or more of a display, a speaker, and a light emitting device such as an LED (Light Emitting Diode).

[0116] The buttons may include, for example, a power button and / or a reset button. The power button is operated, for example, to start and shut down the node 3. The reset (or restart) button is operated, for example, to indicate an intentional reset and / or reconstruction (or restart) of the tree path.

[0117] In addition, the input-output device 34 may have a structure in which input and output are independent. In addition, the input-output device 34 may have a structure in which input and output are integrated, such as a touch panel display.

[0118] Exemplarily, the wireless IF 35 transmits and receives wireless signals in the access line between the terminal device 7. The wireless IF 35 may include, for example, one or more antennas 350, a baseband (BB) signal processing circuit (not shown), a MAC processing circuit, an up-converter, a down-converter, and an amplifier.

[0119] For example, the BB signal processing circuit of the wireless IF 35 may include a coding circuit and a modulation circuit for coding and modulating a transmission signal, and a demodulation circuit and a decoding circuit for demodulating and decoding a reception signal.

[0120] For example, the wireless IF 36 transmits and receives wireless signals in the BH line with other SN 3. Like the wireless IF 35, the wireless IF 36 may include one or more antennas 360, a BB signal processing circuit (not shown), a MAC processing circuit, an up-converter, a down-converter, and an amplifier.

[0121] For example, the BB signal processing circuit of the wireless IF 36 may include a coding circuit and a modulation circuit for coding and modulating a transmission signal, and a demodulation circuit and a decoding circuit for demodulating and decoding a reception signal.

[0122] In addition, the antenna 350 of the wireless IF 35 and the antenna 360 of the wireless IF 36 are sometimes referred to as the "access line antenna 350" and the "BH line antenna 360", respectively. One or both of the access line antenna 350 and the BH line antenna 360 may be an omni-directional antenna (omni antenna) with no directionality or an antenna array capable of controlling directivity. Beamforming can be implemented by an antenna array having a plurality of directional antennas.

[0123] For example, multiple directional antennas may be configured so as to face different directions. For example, six directional antennas may be configured so as to be staggered by 60 degrees. It may also be configured so that when a tree path to be described later is constructed in the BH network 9, when a node 3 has multiple antennas that can communicate with other nodes 3 of the communication object, a wireless connection is established with other nodes 3 through an antenna that exhibits the best communication quality (for example, gain or power), and the antenna continues to be used in the communication of the tree path after the wireless connection is established. However, the antenna used in establishing the wireless connection may be different from the antenna used in the communication of the tree path after the wireless connection is established.

[0124] Exemplarily, the wired IF37 performs wired signal transmission and reception between the wired IF37 and the backbone network 5 and / or the upstream node 3. In addition, exemplary, the wired IF39 performs wired signal transmission and reception between the wired IF39 and the terminal device 7 and / or the downstream node 3. For example, a network interface based on the Ethernet (registered trademark) specification can be used for the wired IF37 and 39. In addition, as long as the wired IF37 is provided at least in CN3, it may not be provided in SN3 (in other words, it may be an option for SN3). However, in the case where a part of the BH line is wired, the wired IF37 and 39 can be used for the wired connection.

[0125] The node 3 may also be configured as hardware including a microprocessor, a DSP, an ASIC, a PLD, an FPGA, etc. For example, the processor 31 may be implemented in a manner including at least one of these hardware. Figure 4 as well as Figure 5 A part or all of each functional block described.

[0126] In addition, "DSP" is the abbreviation of "Digital Signal Processor", "ASIC" is the abbreviation of "Application Specific Integrated Circuit", "PLD" is the abbreviation of "Programmable Logic Device", and "FPGA" is the abbreviation of "Field Programmable Gate Array".

[0127] (Example of Functional Configuration of Node 3)

[0128] Next, refer to Figure 4 as well as Figure 5 , an example of the functional structure of node 3 is described. Figure 4 is a block diagram showing an example of a functional structure of a node 3 according to an embodiment. Figure 5 It is shown Figure 4 A block diagram of an example of a functional structure of a control unit illustrated in FIG.

[0129] like Figure 4 As shown, when focusing on the functional structure, the node 3 may include a wireless communication unit 301 for a wireless access line, a wireless communication unit 302 for a wireless BH line, a wired communication unit 303, a control unit 304, and a storage unit 305.

[0130] The wireless communication unit 301 for the wireless access line includes Figure 3 The wireless IF 35 and the access line antenna 350 are functional blocks shown in the example. The wireless communication unit 302 for the wireless BH line is composed of Figure 3 The functional blocks of the wireless IF 36 and the BH line antenna 360 are exemplified in FIG.

[0131] The wired communication unit 303 includes Figure 3 The memory unit 305 includes the functional blocks of the wired IFs 37 and 39 illustrated in the example. Figure 3 The functional blocks of one or both of the memory 32 and the storage 33 illustrated in the example.

[0132] The wireless communication unit 301 may include, for example: a transmission unit that transmits a control signal and / or a data signal to the terminal device 7 ; and a reception unit that receives the control signal and / or the data signal transmitted by the terminal device 7 .

[0133] The wireless communication unit 302 may include, for example: a transmission unit that transmits a control signal and / or a data signal to other nodes 3 ; and a reception unit that receives a control signal and / or a data signal from other nodes 3 .

[0134] The wired communication unit 303 may include, for example: a transmission unit that transmits a control signal and / or a data signal to the backbone network 5 ; and a reception unit that receives a control signal and / or a data signal from the backbone network 5 .

[0135] The control unit 304 comprehensively controls the operation of the node 3. For example, the control unit 304 supplies a control signal to one or more of the wireless communication unit 301, the wireless communication unit 302, and the wired communication unit 303 to control communication via one or more of the wireless access line, the wireless BH line, and the wired line.

[0136] The control unit 304 performs the following operations, for example: Figure 3 The processor 31 shown is specifically implemented by reading a program stored in the storage unit 305 and executing the read program.

[0137] The storage unit 305 stores, for example, the node identification information and the path metric described below. As described below, when the transmission power value of the transmission source node 3 is not included in the path construction packet, the transmission power value of the transmission source node 3 may be stored in the storage unit 305 .

[0138] (Configuration Example of Control Unit 304)

[0139] like Figure 5 As shown, illustratively, the control unit 304 may include a scan processing unit 341 , a node management unit 342 , a tree path control unit 343 , and a mode setting unit 344 .

[0140] The scanning processing unit 341 scans and finds the existence of other nodes 3 located around (near) the node 3, for example, in response to the activation of the node 3. The scanning can be either passive scanning or active scanning. In the case of passive scanning, a beacon signal is generated in the scanning processing unit 341 and sent to the surrounding area through the wireless communication unit 302.

[0141] In addition, the node 3 that exists at a position where a beacon signal can be received is referred to as a "peripheral node 3" or a "neighboring node 3".

[0142] For example, the beacon signal may include SSID (Service Set Identifier) ​​or BSSID (Basic SSID), information that explicitly or implicitly indicates the beacon signal transmission period and the available channels (frequencies). This information can be simply referred to as "BSS (Basic Service Set) associated information".

[0143] In the case of active scanning, a probe request signal may be generated in the scanning processing unit 341 and sent to the surrounding area through the wireless communication unit 302. The probe request signal is used, for example, to prompt the surrounding nodes 3 to send beacon signals. Active scanning may also be performed when a beacon signal is not received within a certain period of time in passive scanning.

[0144] The node management unit 342 stores information of the neighboring nodes 3 (for example, node identification information and BSS-related information) in the storage unit 305 , for example.

[0145] The tree path control unit 343 controls the construction and update of the tree path by sending and / or receiving a path control packet to the peripheral node 3 .

[0146] For example, when the node 3 is movable, the mode setting unit 344 sets information indicating whether to operate in the "movement mode" (which may be simply referred to as "mode setting information") to the tree path control unit 343.

[0147] In addition, the "mobile mode" may also be referred to as "vehicular mode", and hereinafter, it may be simply referred to as "V mode". In addition, the "non-V mode" may also be referred to as "stationary mode" or "fixed mode".

[0148] SN3 not set to "V mode" is not limited to SN3 explicitly set to mode setting information indicating "non-V mode", and may also include SN3 implicitly set to "non-V mode". For example, SN3 not set to mode setting information indicating "V mode" can be regarded as SN3 implicitly set to "non-V mode".

[0149] For example, when the V mode in SN3 is a special mode and the "non-V mode" is the default (or normal) mode, SN3 can be considered to be set to the "normal mode" unless the mode setting information indicating the "V mode" is set.

[0150] The mode setting information may be provided to the node 3 through, for example, one or more of the input / output device 34, the wireless IF 35, and the wireless IF 36. The mode setting information provided to the node 3 is stored, for example, in the storage unit 305. Once the mode setting information is stored in the storage unit 305, it may be considered that the mode setting is performed for the tree path control unit 343 that refers to the mode setting information.

[0151] The mode setting information may also be pre-stored as static information in the storage unit 305. When the static mode setting information is stored in the storage unit 305, in other words, when the node 3 does not need to change the mode, the function of the mode setting unit 344 of the node 3 may be prohibited (or disabled), and the node 3 may not have the mode setting unit 344.

[0152] For example, since CN3 connected to the backbone network 5 via a wired line can be fixedly set, the function of the mode setting unit 344 of CN3 can be prohibited (or disabled), and CN3 may not have the mode setting unit 344.

[0153] For example, in the case where the SN3 is also known to be fixedly installed and does not need to be moved, the function of the mode setting unit 344 of the SN3 may be prohibited (or disabled), and the SN3 may not have the mode setting unit 344. For the SN3 that is assumed to be moved, rewritable mode setting information may be stored in the storage unit 305.

[0154] The SN3 set to the "V mode" may be a part of the plurality of SN3 forming the BH network 9. For example, in the BH network 9, the SN3 set to the "V mode" and the SN3 set to the "normal mode" may coexist.

[0155] In the following, SN3 set to "V mode" is sometimes abbreviated as "VSN3", and SN3 not set to "V mode" is expressed as "non-VSN3" or "normal SN3". VSN3 performs tree path control so as not to correspond to an "internal node" in the tree path, in other words, to correspond to a "leaf node" without child nodes.

[0156] For example, when receiving a control signal transmitted from CN3 via or without passing through the upstream node 3, the tree path control unit 343 of VSN3 terminates the received control signal and does not (intentionally) further transmit the control signal.

[0157] Therefore, in the tree path control based on the path metric, even if VSN3 sometimes becomes a child node of CN3 or other SN3, it will not become a parent node of other SN3. In other words, VSN3 will not become an internal node of the tree path (in other words, a relay node or an intermediate node).

[0158] Therefore, in the BH network 9, for example, a tree path is constructed or updated by sending a control signal multiple times from CN3 so that VSN3 leaves the internal node and corresponds to a leaf node.

[0159] In addition, since VSN3 becomes a leaf node of the tree path, it is not necessary to perform relay processing like an internal node. Therefore, it is helpful to reduce the power consumption of VSN3. For example, as described below, since terminal device 7 can be used as VSN3, it is possible to reduce the power consumption of terminal device 7. Therefore, it is possible to reduce the battery consumption of terminal device 7 with limited capacity.

[0160] In addition, VSN 3 (including terminal device 7 operating as VSN 3. The same shall apply hereinafter) can join (connect to) the tree path by, for example, receiving a beacon signal transmitted by any SN 3 forming the tree path as described below.

[0161] After joining the tree path, VSN3 receives one or more control signals sent by CN3, determines (selects) and updates the parent node based on the path metric to become a more appropriate entity of the path.

[0162] In addition, VSN3 may transmit (broadcast) a control signal including information indicating that VSN3 is not a candidate parent node, instead of not transmitting the received control signal (control signal for selecting a parent node). SN3 that has received the control signal including this information will not select VSN3 as a parent node. Thus, in the same manner as when VSN3 does not transmit the received control signal, a tree path is constructed or updated so that VSN3 is equivalent to a leaf node.

[0163] (Configuration Example of Tree Path Control Unit 343)

[0164] like Figure 5 As shown in the example in FIG. 3 , the tree path control unit 343 may include, for example, a path control packet generation unit 3431 , a path metric calculation unit 3432 , and a tree path update unit 3433 .

[0165] The path control packet generation unit 3431 generates a path control packet. The path control packet is an example of a control signal generated in CN3 and transmitted to each node 3 in the BH network 9. For example, CN3 floods the control signal to the surrounding nodes 3.

[0166] When receiving the control signal, SN3 (except VSN3) floods the control signal to the surrounding nodes 3. In this way, the control signal transmitted from CN3 is propagated or transferred in sequence or chain in the BH network 9.

[0167] At this time, SN3 other than VSN3 may add information to the control signal to be transmitted to other neighboring nodes 3. A non-limiting example of the information added to the control signal is the path metric calculated by the path metric calculation unit 3432.

[0168] In the case of VSN3, even if a control signal is received, it is terminated without further flooding the control signal.

[0169] Exemplarily, the path control packet may include a path construction packet and a reset packet. The categories of these packets may be identified, for example, by the type value of the packet header.

[0170] The path construction packet is, for example, a packet sent when a tree path is constructed or updated. The path construction packet may cumulatively include the path metrics calculated in each of the nodes 3 that the path construction packet passes through. For example, the node 3 may also include the path metrics from the core node to the node before the node itself in the path construction packet and send it.

[0171] The SN 3 that has received the path construction packet determines a node 3 that is to be a parent node among a plurality of neighboring nodes 3 based on the cumulative path metrics.

[0172] The reset packet is, for example, a packet sent by CN3 when requesting SN3 to clear the tree path. SN3, which receives the reset packet, clears the information of the surrounding nodes 3 registered in the tree path.

[0173] The path metric calculation unit 3432 calculates, for example, a propagation quality index in a wireless section between the neighboring node 3 that is the source of the received path construction packet, and adds the calculation result to the path metric included in the received path construction packet to obtain a new path metric.

[0174] For example, RSSI (Received Signal Strength Indicator) can be used as the propagation quality indicator of the wireless section between the nodes 3. For example, the series of values ​​obtained by uniformly sampling the RSSI between the nodes 3 at a certain time interval is represented as Rn (n is an integer greater than 1), and the successive average (series) An [dB] of RSSI is calculated by the following formula (1). In addition, formula (1) is only an example, and other formulas can also be used to calculate the successive average of RSSI.

[0175] [Formula 1]

[0176]

[0177] The successive average An expressed by equation (1) converges to the average value of the random process as the value of "n" increases. If "n" represents, for example, the number of times the path construction packet is sent (or received) after the reset packet is sent (or received), then the successive average An of the RSSI between the nodes 3 will converge to a certain value as the number of times n increases. Therefore, the tree path constructed by sending the path construction packet will converge to an asymptotically stable path.

[0178] In addition, the path metric calculation unit 3432 can use the successive average An of RSSI calculated by formula (1), for example, to calculate the radio wave propagation loss (path loss) [dB] in the wireless section between the sending source node 3 of the path construction packet by the following formula (2).

[0179] [Formula 2]

[0180]

[0181] In formula (2), "TXPower" represents the transmission power of the transmission source node 3 of the path construction packet. The transmission power value of the transmission source node 3 can be stored in advance in the storage unit 305 as a known value in each node 3, or can be included in the path construction packet at the transmission source node 3.

[0182] Then, the path metric calculation unit 3432 adds the path loss calculated by equation (2) to the cumulative path metric included in the received path construction packet to obtain a new path metric.

[0183] Therefore, the path metric represents the sum of the path losses of the wireless sections between CN3 and one or more SN3. The path metric calculated each time a path construction packet is received is stored in, for example, the storage unit 305. The path metric stored in the storage unit 305 can be initialized to a maximum value, for example, upon reception of a reset packet.

[0184] For example, when the new path metric calculated by the path metric calculation unit 3432 is smaller than the old path metric, the tree path updating unit 3433 selects (updates) the upstream node corresponding to the new path metric as the parent node.

[0185] Here, the constructed tree path has a tree structure, so there must be one upstream node 3 for each SN 3. Therefore, the tree path update unit 3433 can construct or update the tree path by, for example, determining any one of the plurality of peripheral nodes 3 as a parent node.

[0186] For example, the tree path updating unit 3433 determines one of the transmission source nodes (candidate parent nodes) of each control signal received from the upstream direction as the parent node based on the path metric of each path propagated from the plurality of path construction packets received from different paths. Therefore, the tree path updating unit 3433 is an example of a determination unit that determines the parent node.

[0187] In each SN3, the parent node is determined (updated) based on the change in the path metric calculated each time a path construction packet is received. Therefore, by changing the number of times the path construction packet of CN3 is sent per unit time, the tree path update frequency can be changed.

[0188] For example, in an environment where the radio wave propagation environment of the BH network 9 is more likely to change, the number of transmissions of the CN3 path construction packet per unit time is increased, thereby improving the follow-up performance to the change of the radio wave propagation environment of the BH network 9.

[0189] Here, the change in the radio wave propagation environment of the BH network 9 includes the change in the radio wave propagation environment of the wireless section between VSN3 and SN3 (or CN3) as its parent node due to the movement of VSN3. Therefore, as described above, the follow-up performance with respect to the change in the radio wave propagation environment can be improved, which helps to improve the follow-up performance with respect to the movement of VSN3.

[0190] In addition, for example, after the downlink line is established, the child node of the downstream node 3 can be grasped by the positive acknowledgement (ACK) signal received from the downstream node 3. For example, when the downstream node 3 updates the path metric by receiving the path construction packet, it sends (unicast) the ACK signal to the parent node 3 that is the transmission source of the path construction packet. The unicast ACK signal can include, for example, information on the wireless link of the link state stored and managed in the downstream node 3 that is the transmission source of the ACK signal. By receiving the ACK signal from the downstream node 3, the parent node 3 can determine the surrounding node 3 registered as a child node.

[0191] <Action Example>

[0192] Next, an operation example of the above-mentioned wireless communication system 1 will be described.

[0193] Figure 6 This is a diagram showing an example of a tree path constructed by tree path control performed by each of the nodes 3 (for example, eight nodes, ie, node #0 to node #7) constituting the BH network 9.

[0194] Figure 7 It is shown Figure 6 FIG. 4 is a diagram showing an example of tree path control in a case where one (for example, SN#4) of SN#1 to SN#7 forming the tree path is set as the VSN. Figure 8 It is shown Figure 7 A diagram showing an example of tree path control when VSN#4 moves.

[0195] like Figure 7 As shown in the example of (A), when SN#4 is set as the VSN, in the BH network 9, each of the Sns other than VSN#4, namely SN#1 to SN#3 and SN#5 to SN#7, floods the path construction packet from CN#0.

[0196] exist Figure 7In (A), it is assumed that VSN#4 is located in the service area of ​​SN#1 and SN#5. In this case, VSN#4 receives the path construction packets that are flooded by SN#1 and SN#5.

[0197] In response to the reception of the path construction packet, VSN#4 calculates path metrics between, for example, a first path from CN#0 to VSN#4 via SN#1 and a second path from CN#0 to VSN#4 via SN#5.

[0198] Then, VSN#4 selects the upstream node of the path corresponding to each calculated path metric and the old path metric of the first path stored (managed) before the calculation, which has a smaller path metric than other paths, as the parent node, and updates the stored (managed) parent node information. In addition, "parent node information" is sometimes referred to as "parent node information" below.

[0199] For example, when the calculated path metric of the first path is the smallest, VSN#4 selects SN#1, which is the upstream node of the first path, as the parent node. This is an example of a case where the parent node of VSN#4 is not changed even if a new path construction packet is received. There are also cases where the parent node of VSN#4 is changed according to the calculated new path metric.

[0200] Here, as described above, VSN#4 calculates the path metric in response to the reception of the path construction packet, but because it is set to "V mode", it terminates the received path construction packet and does not send a new path metric by flooding the path construction packet.

[0201] So, for example, in Figure 7 In (A), the new path metric is not transmitted to SN#6 which is a child node of VSN#4. SN#6 calculates the new path metric based on the path metric included in the path construction packet received from SN#5, for example.

[0202] In the case where the calculated new path metric is less than the stored (managed) path metric, e.g. Figure 7 As shown in (B), SN#6 selects SN#5 as a new parent node and changes (updates) the parent node information to be managed from SN#4 to SN#6.

[0203] In this way, in the BH network 9, when any one or more SN3 is set as VSN3, the tree path is adaptively updated so that the VSN3 does not correspond to an internal node, in other words, corresponds to a leaf node without child nodes.

[0204] Next, imagine that Figure 7 After the tree path in (B) is updated, for example, Figure 8As shown in (A), VSN#4 leaves the service areas of SN#1 and SN#5 and moves to the service area of ​​SN#6.

[0205] In this case, VSN#4 can receive the path construction packet from SN#6 but not from SN#1 and SN#5. Figure 8 In (A), VSN#4 receives a path construction packet from SN#6 that is sent from CN#0 to SN#6 via SN#1 and SN#5.

[0206] VSN#4, in response to receiving the path construction packet from SN#6, calculates a new path metric and selects parent node 3 based on the new path metric. Figure 8 As shown in (B), VSN#4 selects SN#6 as a new parent node and updates the managed parent node information from SN#4 to SN#6.

[0207] In this way, in the BH network, when VSN3 set to "V mode" moves, the tree path is adaptively updated following the movement of VSN3 by using the path metric calculated based on the path construction packet.

[0208] Here, VSN3 can also be considered to be equivalent to terminal device 7. In other words, terminal device 7 can also be used as SN3, which is the infrastructure of BH network 9. For example, terminal device 7 can act as VSN3 having any one of SN3 constituting BH network 9 at the parent node. Hereinafter, a "terminal device" that acts as a "VSN" is simply expressed as a "terminal device (VSN)".

[0209] For example Figure 8 The movement of VSN#4 shown can be considered as Fig. 9 The movement of the terminal device (VSN) #4 as shown in the example. Figure 8 As described in , a new tree path is constructed (updated) following the movement of the terminal device (VSN) #4. Fig. 9 In the example, the terminal device (VSN) #4 can perform HO (handover or handoff) from the source SN #1 to the target SN #6. Since the same frequency can be allocated to the BH lines in the BH network 9, the terminal device (VSN) #4 can perform soft HO from the source SN #1 to the target SN #6.

[0210] Here, the terminal device (VSN) #4 can be connected to SN #1 or SN #6 as the parent node through the wireless BH line, so it is not necessary to individually allocate a frequency for the wireless access line to the terminal device (VSN) #4. For example, it is allowed to allocate the same frequency to the wireless access line and the wireless BH line.

[0211] Therefore, it is allowed to share, for example, the access line and the BH line without distinguishing between them in the terminal equipment (VSN) 3. Figure 3 The wireless IFs 35 and 36 ( Figure 4 Alternatively, it is possible to reduce one of the wireless IFs 35 and 36 (the wireless communication units 301 and 302). Therefore, it is possible to reduce the size, cost and / or power consumption of the terminal device (VSN) 3.

[0212] In other words, Fig. 9 The system configuration illustrated in the example can be said to be a configuration in which the boundary between the BH line infrastructure and the terminal device is eliminated because the terminal device (VSN) 3 operates as a part of the BH line infrastructure. Fig. 9 The system form illustrated in the example can also be said to be a form in which the wireless access line and the wireless BH line are integrated.

[0213] In cellular communications, in an era where a large number of small base stations that are smaller than micro base stations are arranged in an overlapping manner within a micro base station, infrastructure that enables terminal devices to be used on BH lines as described above is a promising form of post-cellular communications.

[0214] Next, use Figure 10 to Figure 12 The following description will focus on the operation examples of CN3 and SN3. SN3 may include one or both of VSN3 and terminal device (VSN) 3.

[0215] (CN operation example)

[0216] Fig.10 1 is a flowchart showing an example of the operation of CN3 including the tree path control of one embodiment. Fig.10 The flowchart is executed by the control unit 304 of CN3 (for example, the cooperation between the node management unit 342 and the tree path control unit 343).

[0217] like Fig.10 As shown, CN3 monitors whether a specific event is detected (S11: No). The "specific event" may include, for example, CN3 being started, the reset button being operated, and the arrival of a specific timing. An example of a "specific timing" is a transmission timing set for regularly or irregularly transmitting a path control packet.

[0218] When the path control packet is sent periodically, the sending period may be fixed. Since the tree path constructed in this embodiment is asymptotically stable, the sending period may be fixed according to Fig.10In addition, the specified time may be set as the "specific timing" by, for example, updating the tree path according to time periods such as weekends or night and daytime in a day.

[0219] When a specific event is detected ( S11 ; Yes), CN3 generates a path control packet and transmits (floods) the path control packet through, for example, the wireless communication unit 302 ( S12 ).

[0220] For example, when the activation of CN3 is detected and the transmission timing of the route construction packet is detected, the route construction packet is transmitted to the surrounding SN3. When the reset button operation is detected and the transmission timing of the reset packet is detected, the reset packet is transmitted to the surrounding SN3.

[0221] After transmitting the path control packet, CN3 monitors whether the path control packet is received from at least one of the neighboring nodes 3 via the wireless communication unit 302 (S13). Monitoring whether the path control packet is received may also be referred to as waiting for the path control packet to be received.

[0222] When receiving a path control packet from at least one of the neighboring nodes 3 ( S13 ; Yes), CN3 manages the child node ( S14 ) through the node management unit 342 , for example.

[0223] For example, when a route control packet is newly received from the neighboring node 3 of CN3, CN3 stores and registers the node identification information of the source node of the received route control packet in the storage unit 305 as the child node information.

[0224] When the received path control packet is a packet having the node identification information registered in the storage unit 305 as the transmission source, CN3 checks whether the received path control packet is a packet that passes through SN3 different from the registered transmission source.

[0225] For example, as described below, when each of SN3 includes the path metric in the path control packet, by also including the identification information of each node, CN3 can identify the similarities and differences of the paths passed by the received path control packets.

[0226] When the received path control packet is a packet that passes through SN3 different from the registered child node, CN3 may delete the information of the registered child node in the storage unit 305 .

[0227] When the received route control packet is not a packet passing through SN3 which is different from the registered child node, CN3 maintains the information of the registered child node in the storage unit 305 .

[0228] Thereafter, CN3 monitors whether a certain time (for example, the transmission interval of the route control packet) has passed (timeout) (S15). If the route control packet is not received in the process S14 (No), CN3 skips the process S14 and moves the process to S15.

[0229] When a timeout is not detected (S15; No), CN3 shifts the process to S13.

[0230] On the other hand, when a timeout is detected (S15; Yes), CN3 further monitors whether a certain time (for example, the time given to the tree path control) has passed (timeout) (S16), for example.

[0231] When a timeout is not detected (S16; No), the control unit 304 of CN3 shifts the process to S11.

[0232] On the other hand, when a timeout is detected (S16; Yes), the control unit 304 of CN3 ends the tree path control.

[0233] As described above, CN3 repeatedly transmits path control packets and manages child nodes within the given tree path control time, thereby adaptively updating SN3 managed as a child node of CN3 for the tree path with CN3 as the vertex.

[0234] (SN operation example)

[0235] Next, refer to Fig.11 , the action example of SN3 is explained. It can be considered that, Fig.11 The flowchart is executed by the control unit 304 of SN3 (for example, the cooperation between the node management unit 342 and the tree path control unit 343). In addition, SN3 may include one or both of VSN3 and terminal device (VSN) 3.

[0236] SN3 monitors whether a path control packet is received in the wireless communication unit 302, for example (S21; No).

[0237] When the reception of the route control packet is detected (S21; Yes), SN3 checks the type of the route control packet. For example, SN3 checks whether the received route control packet is a reset packet (S22) or a route construction packet (S24).

[0238] When the received path control packet is a reset packet (S22; Yes), SN3 performs initialization processing (S23). The initialization processing may include the following processing, for example.

[0239] · Delete the surrounding node information registered in the storage unit 305

[0240] Initialize the path metric in the storage unit 305 to an initial value (e.g., a maximum value)

[0241] After the initialization process, the control unit 304 transmits (floods) the received reset packet to the surrounding SN3 (S23a). In addition, the reset packet may include an identifier (ID). Each of the nodes 3 may store the ID included in the received reset packet.

[0242] When the ID of the received reset packet matches the stored ID, in other words, when the ID indicates a reset packet that has been sent (forwarded) in the past, each node 3 does not further send the reset packet. This prevents the reset packet from circulating in the BH network 9.

[0243] On the other hand, when the received path control packet is not a reset packet (S22; No), SN3 checks whether the path control packet is a path construction packet (S24).

[0244] When the received path control packet is a path construction packet (S24; Yes), SN3 calculates a propagation quality index (for example, radio wave propagation loss) of the wireless section where the path construction packet is received (S25).

[0245] Based on the calculated radio wave propagation loss, the control unit 304 calculates the path metric (S26). For example, SN3 calculates the cumulative radio wave propagation loss as a new path metric by adding the calculated radio wave propagation loss to the propagation quality index included in the received path construction packet.

[0246] Then, SN3 compares the new path metric with the old path metric stored before calculating the new path metric to determine whether the path metric needs to be updated (S27).

[0247] For example, when the new path metric is smaller than the old path metric, SN3 determines to update the old path metric to the new path metric (S27; Yes). In response to this determination, SN3 selects and updates the upstream node 3 corresponding to the new path metric in the surrounding node information as the parent node (S28).

[0248] After updating the parent node, SN3 checks whether it has been set to "V mode" (S29). If it has not been set to "V mode" (S29; No), SN3 sends a path construction packet including a new path metric to the surrounding SN3 (S30).

[0249] On the other hand, when the "V mode" has been set (S29; Yes), the SN (VSN) 3 skips (in other words, terminates) the process S30 and does not send a route construction packet including a new route metric.

[0250] Thereafter, the control unit 304 monitors whether a certain time (for example, the time given to the tree path control) has passed (timeout) (S31).

[0251] If a timeout is not detected (S31; No), SN3 shifts the process to the process of monitoring the reception of the routing control packet (S21). On the other hand, if a timeout is detected (S31; Yes), SN3 may terminate the tree routing control.

[0252] Furthermore, when the received path control packet is neither a reset packet nor a path construction packet ( S22 ; No, and S24 ; No), SN3 may shift the process to the path control packet reception monitoring process ( S21 ).

[0253] In addition, when the calculated new path metric is greater than the old path metric and it is determined that the parent node does not need to be updated (S27; No), SN3 can also transfer the processing to the reception monitoring processing of the path control packet (S21).

[0254] As described above, SN3 adaptively updates the parent node selected (or managed) in the tree path based on the path metric every time it receives a path construction packet. Therefore, it constructs and updates a more appropriate tree path following changes in the radio wave propagation environment of the wireless section (in other words, the wireless BH line) constituting the BH network 9.

[0255] In addition, when receiving a path building packet, VSN3 will terminate the path building packet and will not send any further path building packets, thus leaving the relay node of the tree path. Therefore, unlike the SN3 in the normal mode, VSN3 does not need to perform the relay processing of packets (which may include both path control packets and data packets). As a result, VSN3 can reduce power consumption.

[0256] (Terminal device joins the tree path)

[0257] Next, use Fig.12 The flowchart illustrates an example of a process in which the terminal device 7 joins the tree path and acts as VSN 3.

[0258] The terminal device 7 monitors whether a beacon signal is received in response to activation (S41: No). Monitoring the reception of a beacon signal may be referred to as waiting for the reception of a beacon signal.

[0259] When receiving the beacon signal, the terminal device 7 stores and manages the included peripheral node information in, for example, the storage unit 305, and also performs an association procedure with the transmission source SN3 of the received beacon signal (S42).

[0260] Through the association process, the terminal device 7 joins the tree path to which the beacon signal transmission source SN3 belongs. Alternatively, the terminal device 7 may wait for the beacon signal to be received in the process S41 by sending a discovery request signal of active scanning to the surrounding nodes 3.

[0261] After the terminal device 7 joins the tree path, Fig.11 The flowchart shown in the example is performed (S43). For example, Fig.11 As described in , terminal device 7, like VSN 3, adaptively updates the parent node selected (or managed) in the tree path based on the path metric each time a path construction packet is received.

[0262] In addition, the process of updating the selected parent node after joining the tree path by the terminal device 7 is not limited to being performed by receiving the path construction packet, but can also be performed by receiving the beacon signal. The beacon signal can be sent at a higher frequency than the path construction packet. In this case, the opportunity (in other words, frequency) of the terminal device 7 to select and update the parent node can be increased.

[0263] In addition, the terminal device 7 Fig.11 In the process S29 of , it is determined that the "V mode" is set (yes), so the path construction packet containing the new path metric is not sent (skipped). The setting of the "V mode" of the terminal device 7 can be performed, for example, by receiving a beacon signal from the surrounding node 3, or in the joint process of the process S42.

[0264] As described above, the terminal device 7 operating as the VSN 3 performs the association process with the SN 3 that has received the beacon signal among the plurality of SN 3 constituting the BH network 9 , and can therefore quickly join the BH network 9 .

[0265] After receiving the path construction packet and determining the parent node based on the path metric, the terminal device 7 terminates the received path construction packet and does not send any further received path construction packets. Thus, each time CN3 sends a path construction packet, the terminal device 7 adaptively updates the tree path so that it does not correspond to a relay node.

[0266] Therefore, since the terminal device 7 does not need to perform packet relay processing, it is possible to reduce power consumption of the terminal device 7. As a result, it is possible to reduce battery consumption of the terminal device 7 having limited capacity.

[0267] Description of Reference Numerals

[0268] 1: Wireless communication system

[0269] 3: Wireless Node

[0270] 5: Backbone network

[0271] 7: Terminal device

[0272] 9: Backhaul (BH) network

[0273] 31: Processor

[0274] 32: Memory

[0275] 33: Memory

[0276] 34: Input and output (I / O) devices

[0277] 35, 36: Wireless interface (IF)

[0278] 37, 39: Wired Interface (IF)

[0279] 38: Bus

[0280] 301, 302: Wireless Communication Department

[0281] 303: Wired Communications Department

[0282] 304: Control Department

[0283] 305: Storage

[0284] 341: Scanning Processing Department

[0285] 342: Node Management Department

[0286] 343: Tree path control unit

[0287] 344: Mode setting unit

[0288] 350, 360 antenna

[0289] 3431: Path control packet generation unit

[0290] 3432: Path metric calculation unit

[0291] 3433: Tree Path Update Unit

Claims

1. A wireless path control method, characterized in that: The following steps are involved: sending, from a first wireless node among a plurality of wireless nodes constituting a backhaul network, a control signal for selecting a parent node in a tree path; Each of a plurality of second wireless nodes different from the first wireless node among the plurality of wireless nodes selects one of the transmission source nodes of each of the plurality of control signals as a parent node based on an indicator indicating a radio wave propagation quality of a path propagated from each of the plurality of control signals received from different paths; The fixed wireless node among the plurality of second wireless nodes sends the received control signal to other second wireless nodes; as well as The mobile wireless node of the plurality of second wireless nodes terminates the received control signal, The first wireless node, the fixed wireless node and the mobile wireless node use a common frequency for wireless communication. The mobile wireless node switches from a first fixed wireless node to a second fixed wireless node in the common frequency.

2. The wireless path control method according to claim 1, wherein: The first wireless node sends the control signal multiple times, Each of the fixed wireless nodes and the mobile wireless nodes among the plurality of second wireless nodes updates the selection of the parent node according to a change in the indicator calculated each time the control signal transmitted a plurality of times is received.

3. The wireless path control method according to claim 1 or 2, wherein: The mobile wireless node is a user device.

4. The wireless path control method according to claim 3, wherein: When the user device receives the beacon signal transmitted by any one of the first wireless node and the second wireless node, the user device joins the backhaul network by performing a linkage process with the transmission source node of the beacon signal.

5. A wireless communication system, characterized in that: include: a first wireless node, the first wireless node being a first wireless node among a plurality of wireless nodes constituting a backhaul network and transmitting a control signal for selecting a parent node in a tree path; as well as a plurality of second wireless nodes, the plurality of second wireless nodes being a plurality of second wireless nodes different from the first wireless node among the plurality of wireless nodes, and determining one of the sending source nodes of each of the plurality of control signals as a parent node based on an indicator indicating the radio wave propagation quality of the path propagated from each of the plurality of control signals received from different paths, The fixed wireless node among the plurality of second wireless nodes sends the received control signal to other second wireless nodes, The mobile wireless node of the plurality of second wireless nodes terminates the received control signal, The first wireless node, the fixed wireless node and the mobile wireless node use a common frequency for wireless communication. The mobile wireless node switches from a first fixed wireless node to a second fixed wireless node in the common frequency.

6. A wireless node, the wireless node being one of a plurality of second wireless nodes different from the first wireless node among a plurality of wireless nodes constituting a backhaul network, characterized in that: include: a setting unit, which sets information indicating whether the second wireless node can be moved into a storage unit; A receiving unit, receiving a control signal sent by the first wireless node for selecting a parent node in a tree path; a determination unit that determines one of the transmission source nodes of each of the plurality of control signals received from different paths as a parent node based on an index indicating the radio wave propagation quality of the path propagated from each of the plurality of control signals received from different paths; and a transmitting unit that transmits the received control signal when the information does not indicate that the movement is possible, and terminates the received control signal when the information indicates that the movement is possible, The receiving unit and the transmitting unit perform wireless communication using a common frequency with the first wireless node and the second wireless node, and switch from a first fixed wireless node to a second fixed wireless node among the plurality of second wireless nodes in the common frequency.

7. A storage medium, characterized in that A wireless path control program is stored, wherein the wireless path control program causes a processor included in one of a plurality of second wireless nodes different from the first wireless node among a plurality of wireless nodes constituting a backhaul network to execute the following processing: setting information indicating whether the second wireless node is movable into a storage unit; receiving a control signal sent by the first wireless node for selecting a parent node in a tree path; Based on an indicator indicating the radio wave propagation quality of a path propagated from each of the plurality of control signals received from different paths, determining one of the transmission source nodes of each of the plurality of control signals as a parent node; If the information does not indicate that the device is capable of moving, the received control signal is sent; if the information indicates that the device is capable of moving, the received control signal is terminated; wirelessly communicate using a common frequency with the first wireless node and the second wireless node; as well as In the common frequency, a handover is performed from a first fixed wireless node to a second fixed wireless node among the plurality of second wireless nodes.

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